LONDON, England (CNN) -- King Abdullah of Saudi Arabia has begun his visit to the UK as controversy continues over issues related to the Middle Eastern kingdom.

King Abdullah is greeted by Britain's Prince Charles at Heathrow Airport.

Queen Elizabeth and British Prime Minister Gordon Brown met the king at London's Horseguards Parade parade ground, ahead of a full state banquet at Buckingham Palace.

Brown will hold talks with King Abdullah at Downing Street Wednesday before the king's departure Thursday.

The UK government regards the state visit, the first in two decades, as being of fundamental importance due to Saudi Arabia's involvement in hot issues such as the war on terror, the situation in both Iran and Iraq and the attempt to broker peace between Israel and the Palestinians.

But the visit has attracted controversy in the UK from activists on a number of issues.

Human rights groups have called on the UK government to react to allegations about the treatment of women and the gay community in the Saudi kingdom, while other protesters have attacked the failure of the Serious Fraud Office investigation into alleged bribes surrounding arms deals.

The Press Association reported that around 100 demonstrators lined The Mall, the approach to Buckingham Palace, shouting at the procession as it passed by.

Peter Tatchell, a human rights campaigner, told the agency that the UK government was showing "incredible hypocrisy" for making no comment about alleged abuses in Saudi Arabia while condemning events in Myanmar and Zimbabwe.

"It just shows oil and arms sales seem to have bought the Government's silence," the agency reported him as saying.

There have also been allegations by Policy Exchange, a think tank, that organizations linked to the Saudi authorities have promoted Islamic fundamentalist literature in UK mosques. Watch how royal visit has stirred anger. »

Vince Cable, acting leader of opposition party the Liberal Democrats, has already announced he will not attend events associated with the visit, while several ministers from Brown's ruling Labour party are expected to join a human rights protest outside the Saudi embassy Wednesday.

King Abdullah stirred controversy ahead of his visit Monday, accusing British authorities of ignoring intelligence that could have prevented the 2005 London bombings

In an interview with the British Broadcasting Corporation, the Saudi king said Britain failed to act on information provided by Saudi security services ahead of the suicide bombings on London's transport network in July 2005 that killed 52 people and injured more than 770.

"We sent information to Great Britain before the terrorist atrocities in Britain, but unfortunately no action was taken and it may have been able to avert the tragedy," the monarch told the BBC.

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He refused to elaborate on the details of the intelligence, saying that disclosing specific information "may cause sensitivities" between the two countries' security services.

A British Home Office spokesman strenuously denied that any intelligence from Saudi Arabia had been overlooked in the run-up to the atrocities and that information provided by the Saudis "was materially different from what actually occurred on 7 July and clearly not relevant to those acts."

"We have made it clear that if we had intelligence that could have prevented the attacks we would have acted upon it," the spokesman told CNN. He also cited a parliamentary investigation last year that found no evidence that intelligence, passed on by the Saudis, could have prevented the bombings.

British Foreign Secretary David Miliband pulled out of a meeting with his Saudi Arabian counterpart in London Monday, but the Foreign Office insisted it was for personal reasons and not a snub. Miliband has just adopted a baby son and is taking time off to look after him, the British Foreign Office confirmed to CNN.

Miliband's duties were being carried out by junior ministers in his absence.E-mail to a friend